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1.
间断区间时态逻辑的语义   总被引:1,自引:0,他引:1  
张师超  张钹 《计算机学报》1996,19(12):949-952
区间逻辑不能模拟自然语言中与,或,非时态关系,其公理系统的完备性不易保证。我们建立的间断区间时态知脚注可以克服区间逻辑的上述缺点,本文给出了间断区间逻辑的语法,语义及公理,即描述了间断区间时态逻辑的语义。  相似文献   

2.
不确定时态信息表示的统一模型   总被引:7,自引:0,他引:7  
时态信息表示和推理是人工智能研究中的一个重要课题,现有的模型大多只能表示确定时态信息,然而现实生活中很多事件的发生结束等时态信息都是不确定的。故提出了一个表示不确定时态信息的统一模型,可用于描述各种具有确定或不确定时态信息的事件。该模型首先定义各类时态对象(如时间点、时间区间)以及它们之间的关系,并给出时态对象间的传递关系表,利用该表能进行时态一致性约束满足问题的求解。最后,给出了两个不确定时态推理的例子,表明了该模型的实际应用意义。  相似文献   

3.
杨倩  冯志勇  胡静 《计算机应用》2010,30(8):2029-2033
通过间断区间的时态理论扩展了OWL-Time,用在本体中表达单个事件带间断时区的情况。在本体中定义了间断区间概念以及间断区间的时态关系,并以物流领域运输事件的表示为例阐述了领域中基于间断区间的时间知识在本体中的表示方式。通过定义Jena中的原语、规则以及扩展对推理模型的操作构建了相应的推理机,对推理机进行实验检验,不仅验证了推理机运行的正确性,同时也保证了时间知识在本体和规则中表示的正确性,解决了带间断区间的时态知识在语义网中表示和推理的问题。  相似文献   

4.
莫孙冶  林嘉宜  彭宏 《计算机工程》2005,31(18):197-199
研究不确定时间具有广泛的应用.不确定时间常常表现出模糊性,该文用模糊集的方法研究不确定时间点、不确定时间区间的表示方法及其时态关系.  相似文献   

5.
首先介绍已有的时态关系表示方法,并比较各时间模型的特点,在此基础上,结合多媒体开发实例提出媒体时态关系表示在多媒体应用程序制作过程中的应用。  相似文献   

6.
马慧  汤庸  潘炎 《计算机工程》2006,32(17):132-134
随着各种形式的数据的迅速增长,业务数据中的时态信息挖掘问题受到人们普遍关注。该文提出了一种带有效时间区间的时态关联规则,给出了一种基于FP-树的挖掘方法。该方法利用分区挖掘的思想,以分区为单位表示项集的有效时间区间,并为每个分区构建FP-树,大大简化了对某个项集在其有效时间区间中的出现次数的计算,从而更有效地计算时态置信度。最后用一个例子对该方法的执行过程进行了阐述。  相似文献   

7.
针对应急决策中的不确定性,在传统区间代数方法的基础上,采用对区间时间断点模糊化处理并设定其取值范围的方法实现了应急领域不确定时态知识的表达,在此基础上,研究时态推理中的证据合成,通过时间区间集合,时态关系集合以及概率指派函数合成后的更新,给出了解决方案,结合应用算例进行分析。验证了该方法的有效性。  相似文献   

8.
左亚尧  舒忠梅  汤庸 《软件学报》2014,25(10):2312-2324
时态跨度是时态应用中重要但又非常特殊的时态原语:一则,在不同的时态上下文中,其语义内涵往往呈现出不确定性;再者,其灵活的刻画形式又表现出一些不规范性,使得时态应用中难以有效地驾驭其序关系,影响时态运算的精确性。从时态跨度的序关系入手,分析了时态跨度绑定操作的必要性,提出了通过将时态原语和时态跨度映射到仿射空间中,利用仿射变换构建时态跨度绑定的方法,并实现了与时态粒点、非间断时态粒区、间断时态粒区间的绑定和运算。  相似文献   

9.
不明确时间间隔的表示及时态运算的扩展   总被引:2,自引:1,他引:2  
贾超 《计算机工程》2002,28(8):123-134,237
讨论了时态数据库处理不明确时间存在的一些问题,并给出描述不明确时间间隔的表示方法,在此基础上给出了各种时态运算的扩展,丰富了时态数据库的适应性。  相似文献   

10.
时态表示和推理是人工智能领域的重要研究内容之一,它的应用范围分布很广,从逻辑基础研究到知识系统的应用。区间代数是一种独立的与领域无关的时态理论。用区间代数能表示不确定的时态关系,可以很方便的用于时态推理,表达能力强;时态关系的区间表示比较直观,可理解性强;同时区间代数可以进一步扩展到二维空间领域,即将区间代数拓展为矩阵代数,实现二维空间推理。在一维时态推理中,将时态的区间表示和矩阵表示相结合,在提高计算效率的同时,保持了形象直观的时态表示。  相似文献   

11.
We investigate a formal representation of time units , calendars , and time unit instances as restricted temporal entities for reasoning about repeated events. We generalize Allen's interval relations to a class level, and based on interval classes we define time units. We examine characteristics of time units, and provide a categorization of the hierarchical relations among them. Hence we define an abstract hierarchical unit structure (a calendar structure ) that expresses specific relations and properties among the units that compose it. Specific objects in the time line are represented based on this formalism, including nonconvex intervals corresponding to repeated events. A goal of this research is to be able to represent and reason efficiently about repetition in time.  相似文献   

12.
刘婷  林闯  刘卫东 《计算机学报》2002,25(6):637-644
该文在扩展时段时序逻辑的基础上提出了一种推理机制,这种推理机制基于时间Petri网模型及基本不等式规则,可由一组已知的扩展时段时序关系推出一些未知的扩展时段时序关系,对不确定时间段内发生的事件及其相互关系具有较好的描述能力,这种推理机制的优势在于定性地对扩展时段之间的时序关系进行推理分析,利用时间Petri网模型,可以对复杂时序逻辑关系进行化简,比单纯利用不等式规则的推理更直观,也更简单,是一种行之有效的方法。  相似文献   

13.
This study was motivated by some difficulties encountered by the authors when trying to express temporal knowledge using Sowa's conceptual graph (CG) approach. An overview of Sowa's approach is given and the difficulties encountered when trying to model temporal knowledge are outlined: the disparity of notations allowed by CG theory for expressing temporal information; the ambiguity and incompleteness of tense sspecification; the difficulty of harmonizing tenses and intergraph temporal relations. Various approaches suggested for representing time both in artificial intelligence and linguistics are presented, and an extension to Sowa's approach is proposed in which temporal and nontemporal knowledge are differentiated. In this model points in time are represented as well as time intervals. A semantic interpretation of verbs is provided based on an extension of Reichenbach's model of temporal markers. The authors show how their approach enables the representation of tenses as well as the aspectual properties of natural language sentences.  相似文献   

14.
Applications using expert systems for monitoring and control problems often require the ability to represent temporal knowledge and to apply reasoning based on that knowledge. Incorporating temporal representation and reasoning into expert systems leads to two problems in development: dealing with an implied temporal order of events using a non-procedural tool; and maintaining the large number of temporal relations that can occur among facts in the knowledge base. In this paper we explore these problems by using an expert system shell, CLIPS (C Language Integrated Production System), to create temporal relations using common knowledge-based constructs. We also build an extension to CLIPS through a user-defined function which generates the temporal relations from those facts. We use the extension to create and maintain temporal relations in a workflow application that monitors and controls an engineering design change review process. We also propose a solution to ensure truth maintenance among temporally related facts that links our temporal extension to the CLIPS facility for truth maintenance.  相似文献   

15.
The standard AI method for representing temporal information in a first‐order logic is to directly associate the information with a time point or interval via a relation. We present a new paradigm for temporal knowledge representation. All point‐based temporal information is translated to real‐valued functions in the Cartesian plane. For example, information that is true/false at a point becomes a 0–1 function. Other types of information, such as velocity, are directly represented with real‐valued functions. The unique feature of the proposed approach is the use of the Riemann integral to represent interval‐based information. Our approach is based on the fact that what is true at every point in an interval completely determines what is true over the interval. We conclude with a formal presentation of a first‐order logic that is based on the proposed representation.  相似文献   

16.
林闯  刘婷  曲扬 《计算机学报》2001,24(12):1299-1309
针对点-时段时序逻辑的不足,提出了一种新的时段时序逻辑--扩展时段时序逻辑,对不确定时间段发生的事件具有较好的描述能力。时间Petri网模型表示的引入,增强了扩展时段时序逻辑的描述直观性及分析能力,为进行线性推理提供了有利的工具。同时还提出了几种变迁间的实施推理规则。运用这些规则可以简化复杂时序关系的Petri网模型,并在线性时间复杂度内定量地得到各变迁间的时序逻辑关系,因而是一种行这有效的方法。  相似文献   

17.
A knowledge hypergraph is a form of heterogeneous graph representing the real world through $n$-ary relations, but existing knowledge hypergraphs are usually incomplete in both general and vertical domains. Therefore, it is challenging to infer the missing links from the existing links in knowledge hypergraphs. Most of the current studies employ knowledge representation learning methods based on $n$-ary relations to accomplish link prediction in knowledge hypergraphs, but they only learn the embedding vectors of entities and relations from time-unknown hyperedges without considering the influence of temporal factors on the dynamic evolution of facts, which results in poor prediction performance in dynamic environments. Firstly, based on the definition of temporal knowledge hypergraphs proposed by this paper for the first time, this paper puts forward a link prediction model for temporal knowledge hypergraphs and learns static and dynamic representations of entities from their roles, positions, and timestamps of temporal hyperedges. Then these representations are merged in a certain proportion and utilized as final entity embedding vectors for link prediction tasks to realize the full exploitation of hyperedge temporal information. Meanwhile, it is theoretically proven that the proposed model is fully expressive with linear space complexity. Additionally, a temporal knowledge hypergraph dataset CB67 is constructed from the public business data of listed companies, and a large number of experimental evaluations are conducted on this dataset. The experimental results show that the proposed model can effectively perform link prediction tasks on the temporal knowledge hypergraph dataset.  相似文献   

18.
Due to increasing interest in representation of temporal knowledge, automation of temporal reasoning, and analysis of distributed systems, literally dozens of temporal models have been proposed and explored during the last decade. Interval-based temporal models are especially appealing when reasoning about events with temporal extent but pose special problems when deducing possible relationships among events. The paper delves deeply into the structure of the set of atomic relations in a class of temporal interval models assumed to satisfy density and homogeneity properties. An order structure is imposed on the atomic relations of a given model allowing the characterization of the compositions of atomic relations (or even lattice intervals) as lattice intervals. By allowing the utilization of lattice intervals rather than individual relations, this apparently abstract result explicitly leads to a concrete approach which speeds up constraint propagation algorithms.  相似文献   

19.
A discourse is composed of a sequence of sentences that must be interpreted with respect to the context in which they are uttered and to the actions that produce them: locutors' speech acts. The analysis of discourse content must be based on a pragmatic approach to the study of language in use. Some of the most obvious linguistic elements that require contextual information for their representation are deictic forms such as here, now, I, you, this , and verb tenses.Several authors have recognized a need for introducing contextual structures in knowledge representation models such as semantic networks. Sowa's Conceptual Graph Theory is a powerful approach to conceptually represent knowledge contained in discourses. However, it must be extended in order to represent several semantic and pragmatic mechanisms related to the expression of time in natural language. In this paper we present such an extension as a framework for modeling temporal knowledge in discourses integrating several features borrowed from speech act theory.First, we introduce the notions of time interval, temporal object, temporal situation, and temporal relation. Then, we discuss the importance of explicitly introducing the concept of time coordinate system in a discourse representation and we present different kinds of temporal contexts: narrator's perspective, agent's perspective and temporal localization. We show how this conceptual framework can be used to represent various referential mechanisms in discourse such as anaphoras, indexicals, direct and indirect styles. We also discuss how to model several linguistic phenomena such as speech act characteristics and the specification of performative and attitude utterances. Finally, we briefly discuss how verb tenses can be determined in a discourse on the basis of this temporal approach.  相似文献   

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